Wrist biomechanics in 3-D local coordinate space during wheelchair propulsion

The purpose of this paper is to describe the development and testing of a 3-D local coordinate system for assessing wrist biomechanics during wheelchair propulsion. Vectors centered at the ulnar styloid define planes of the wrist and thus flexion/extension, radial/ulnar deviation, and supination/pronation can be determined. The three predominant forces occurring during the propulsion phase are a shear force acting from radial to ulnar styloid, a shear force acting from palmar to dorsal surface, and a compressive force acting along the long axis of the wrist and forearm. The largest moment acts in the direction of ulnar deviation, not flexion or extension. This study demonstrates the importance of using a 3-D local coordinate space for assessing wrist kinetics during wheelchair propulsion and further work will provide insight into possible injury mechanisms.